Throughout this application various publications are referenced and citations are provided in parentheses for them. The disclosures of these publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art to which this invention pertains.
Propolis, a popular "folk medicine" purported to have therapeutical benefit, is a brownish mass produced by honeybees in their hives. A significant number of so-called "folk medicines" have withstood scientific scrutiny, with many of their purported therapeutic benefits being attributable to distinct chemical entities. Such naturally derived compounds often produce fewer and less serious side effects as compared to analogous man-made pharmaceuticals; unfortunately, most are chemically complex, not lending themselves to economically feasible syntheses. Propolis, is alleged to exhibit a broad spectrum of activities. It is marketed in health stores as a natural antibiotic (F. B. Wells, Am. Bee J. 116, 512 (1976) (a review of the antimicrobial effects of propolis)); aqueous extracts are sold in Europe as a cough syrup and sore throat remedy; compacts prepared from it are used to treat skin inflammations (Apimondia, A Remarkable Hive Product: Propolis, Bucharest, 1978); ingestion of raw propolis is reputed to clear sinuses and treat viral infections (E. L. Chisalberti, Bee World 60, 59 (1979)); and propolis has been used to arrest the growth of tumors. Propolis is a conglomeration of compounds mostly derived from plant sources, and is rich in waxes, resins, oils, pollen (J. Cizmarik, I. Matel, Experentia 15, 713 (1970)), flavonoids (V. S. Bankova, S. S. Popov, N. L. Marekov, J. Nat. Prod. 46, 471 (1983)), and polyphenolic acids (J. Cizmarik, supra). Together these substances provide properties which permit its natural use by the honeybee as a hive cement or glue (G. Toth, Am. Bee J. 125, 337 (1985)).
Some of the observed biological activities may be traced to identified chemical constituents such as caffeic acid (J. Cizmarik, supra), which is a reported antimicrobial and anti-inflammatory agent (V. S. Bankova, supra). However, it is difficult to generalize such relationships since the composition of propolis varies with the flora of a given area, the time of collection and contaminants from collection (G. Toth, supra). Ethyl ether extracts of propolis have previously been demonstrated to be cytostatic to KB and HeLa cell lines (B. Hladon et al., Arzneim-Forsch./Drug Res. 30, 1847 (1980)), however the components responsible for this interesting activity were not defined.
The invention described herein concerns a compound present in propolis which is at least partially responsible for its reported cytostatic properties. It represents the most active component as judged by the assay employed in its study (cytostatic towards Ltk.sup.- cells). The compound has been identified as caffeic acid phenethyl ester (CAPE) and a one-step synthesis method has been developed which is amenable to large scale preparation. Through investigations of CAPE's cytostatic properties uncovered several differential effects. For example, human tumor cell lines displayed a significantly greater sensitivity to the action of CAPE than analogous normal lines. Additionally, CAPE has been found to possess anti-inflammatory activity. Phenethyl alcohol and caffeic acid, the most obvious metabolic products of CAPE, displayed none of the aforementioned activities.